Cigarette paper



United States Patent CIGARETTE PAPER Walter G. Frankenburg,Millersville, Pa., assignor to General Cigar Co., Inc., New York, N. Y.,a corporation of New York No Drawing. Application December 4, 1953,,Serial No. 396,326

9 Claims. (Cl. 131-45) This invention relates to an improved cigarettepaper.

In recent years, the cigarette industry has given considerable attentionto undesirable components in cigarette smoke and efforts to minimize orovercome the objectionable characteristics of cigarette smoke haveresulted in two widespread trends in cigarette manufacture, namely, theaddition of filter elements in cigarettes and the production ofextra-long or king-size cigarettes. The theory is that the material inthe filter element or in the additional length of a king-size cigaretteabsorbs some of the undesirable components of the cigarette smoke as itis drawn through the cigarette by the smoker so that these componentsare removed or filtered .out from the smoke reaching the smokers mouth.These trends have increased the cost of cigarettes without providingcompletely satisfactory elimination of the troublesome components ofcigarette smoke.

Tests with cigarette paper alone have revealed that when cigarette paperburns slowly as in a cigarette, the smoke evolved by the burning paperis distinctly acrid and irritating to the nose and throat. Thesefindings are unexpected because, theoretically, burning paper, which isessentially cellulosic material, yields only carbon dioxide and watervapor which are inert and not obnoxious. Apparently, what actuallyhappens is that the portion .of the celiulosic material contiguous tothe glowing and burning portion of the cigarette paper .undergoesthermal decomposition with generation of acidic gaseous materials thatdiffuse away and thus escape combustion.

The principal objectof this invention is to provide an improvedcigarette paper that on burning yields a smoke substantially free ofobnoxious components.

A further important object is to provide cigarette paper with modifiedburning characteristics so that the generation of disagreeable gasesduring combustion is substantially eliminated.

Other features of the invention will be apparent in the descriptionwhich follows.

In accordance with this invention, cigarette paper which is essentiallycellulosic material in fiber form has intimately associated therewith afinely divided, mineral-type, siliceous catalyst which beingincombustible and refractory remains substantially unchanged duringcombustion of the cigarette paper and functions like a catalyst inmodifying the combustion of the paper so that the resultant combustiongases and vapors are substantially free of the undesirable componentsformed when cigarette paper is burned in the absence of the siliceouscatalyst.

Typical suitable siliceous catalysts are acid-treated clays,heat-treated montrnorillonite, and natural and synthetic silicatescontaining some hydrogen atoms which are relatively mobile. Inasmuch asthese siliceous'materials survive the combustion of the cigarette paperas particulate solids while exerting a favorable influence on theburning of the cellulosic content of the cigarette paper, I believe thatthey act as catalysts in the sense that the usual aldehydic or acidic orhydrocarbon-type products 2,755,207 Patented July 17, 1956 2 ofcombustion are not at all formed or, if formed, are promptly furtheroxidized to the harmless form of carbon dioxide and water vapor so thatthe smoker observes no foreign taste or odor.

Tests with various siliceous catalysts have revealed a strikingparallelism between their effectiveness for the purposes of thisinvention "and their effectiveness as petroleum cracking catalysts. Inshort, there is a Well defined trend indicating that a siliceouscatalyst which is good for cracking hydrocarbons is good for avoidingthe development of objectionable smoke components in cigarette paper. Infact, I have prepared distinctly superior cigarette paper which onburning is free of obnoxious gaseous products by incorporating thereinsiliceous catalysts selected merely on the basis that they were known tobe successful cracking catalysts of the petroleum refining industry.This surprising discoverymay indicate that the pyrogenic decompositionproducts of the cellulosic material in cigarette paper are similar, oridentical with, hydrocarbons and that the function of the siliceouscatalyst consists in cracking these hydrocarbons into smaller molecularunits which are then readily and completely oxidized to carbon dioxideand water vapor.

it is today generally accepted that a certain acidic nature is essentialfor the effectiveness of catalysts for cracking of high molecularhydrocarbons to lower molecular fragments. This property also seems tobe a prerequisite for the efficiency of the siliceous catalysts usedpursuant to my invention for the improvement of the smoke developed inburning cigarette paper. A class of catalysts with the proper acidicnature which can be used is that of solid particles containing silicaand such amounts of ditficultly reducible metal oxides that themolecular ratio of silica to the other oxides exceeds appreciably thevalue of 1. As all these combinations of silica with other oxides, suchas for instance, alumina, zirconia, titania, chromium oxide, magnesiumoxide and others, contain small amounts of water, it is quite likelythat the solid phase comprises a kind of complex acid in which somehydrogen atoms are in a rather mobile state especially at the surface ofthe solid particles. This view and experimental support for it have beenpre- Sented by R. C. 'Hansford in a paper entitled, A mechanism ofcatalytic cracking, "Ind. and Eng. Chem., 39, 849 1947). The specificcatalyst mentioned in this paper was composed of approximately 12%alumina and 88% silica (on dry basis). In another paper entitled,Montmorillonite cracking catalyst, Ind. and Eng. Chem., 41 148 5 (1949),Alexander G-renall has demonstrated the presence of hydrogen ion inFiltrol clay catalysts.

Silica gels which have been impregnated, even with as little as 1%alumina, have been shown to be efficient cracking catalysts by Pitzer inAdvancing Fronts in Chemistry, vol. 1, page 33, 1945, "Rhein'holdPublishing Corp. Another cracking catalyst has been described by OKellyet al. in ind. and Eng. Chem, 39, 154 (1947), as being prepared by theco-precipitation of the hydrous oxides of silicon and aluminum in aweight ratio of 9:1 of silica to alumina. A tri-component crackingcatalyst consisting of silica, alumina and zirconia has been describedby Thomas et al. in J. Am. Chem. Soc., 66, 1694 (1944).

Cracking catalysts can be prepared by using natural clays as a startingmaterial. Many clays contain silica and alumina in a ratio whichcorresponds to the postulate that the number of moles of silica exceedappreciably the number of moles of alumina or other oxide. However, someof these clays contain, instead of mobile hydrogen atoms combined withexcess silica, other atoms, such as alkali and alkaline earth atoms.Such clays can be activated by removing part or all of the alkali andalkaline earth atoms and replacing them with hydrogen atoms by treatmentwith acid. Other clays, which already in their original composition havea potential acidic nature by having the proper ratio of silica toalumina or other oxides, can be activated by heat treatment (cf.Alexander Grenall l. c.).

All of the aforementioned natural and synthetic cracking catalysts areeffective siliceous catalysts for the purposes of this invention. Torecapitulate, my siliceous catalyst is a combination of a major weightproportion of silica and a minor weight proportion of one or moredifficulty reducible metal oxides; this combination may be effectedsynthetically or it may be derived from natural materials like claysthrough activation by heat and/or acid treatment.

The finely powdered siliceous catalyst can be incorporated in thecigarette paper in various ways and at ditfercnt stages of themanufacture of the paper. For instance, since the powdered siliceouscatalyst used in this invention is insoluble, it may be dispersed in theaqueous pulp of cellulosic fibers from which the paper is made or it maybe added while the cigarette paper is being formed from the pulp.Alternatively, the catalyst may be applied to the surface of thecigarette paper; calendering or a small amount of adhesive such asmethyl cellulose may be used to improve the adhesion of the powderedcatalyst deposited on the paper. In any event, the siliceous catalyst isbrought into close and uniform association with the fibrous cellulosiccontent of the cigarette paper so that the latter may subsequently beburned without evolving unpleasant combustion products.

The quantity of siliceous catalyst used in cigarette paper in accordancewith this invention depends upon the efiicacy or activity of the chosensiliceous catalyst. in general. the addition of the siliceous catalystfalls in the approximate range of 20% to 60% based on the weight ofcellulosic material in the cigarette paper. Preferably. siliceouscatalysts, like good hydrocarbon cracking catalysts, are usuallyemployed in the proportion of about 45% to 55% based on the weight ofcellulosic material.

In an illustrative embodiment of the invention, the fibrous ccllulosicpulp for a conventional cigarette paper is uniformly admixed with afinely powdered siliceous catalyst (passing through a ZOO-mesh sieve)which is a silica gel containing about 11% by weight of alumina (groundSovabead catalyst of Socony-Vacuum Company). The quantity of catalystused corresponds to approximately 50% by weight of the dried cellulosicmaterial in the pulp. The fibrous pulp containing the admixed siliceouscatalyst is then formed into cigarette paper in the usual manner. Testsin which the catalystcontaining paper is burned slowly reveal that thegaseous products of combustion are mild and not disagreeable whereasidentical tests with cigarette paper made from the same pulp without theaddition of the siliceous catalyst yield combustion gases that aredistinctly obnoxious and irritating to the nose and throat.

This application is a continuation-in-part of my copending applicationSerial No. 105,660, filed July 19, 1949, now matured as U. S. Patent No.2,706,695, issued April 19, 1955, which discloses the use of the samesiliceous catalysts, herein discussed, in smoking products made withwater-soluble cellulose derivatives such as methyl cellulose and thesodium salt of carboxymethyl cellulose.

Those skilled in the art will visualize many other modifications andvariations of the invention set forth hereinabove without departing fromits spirit and scope. Accordingly, the claims should not be interpretedin any restrictive sense other than that imposed by the limitationsrecited within the claims.

What is claimed is:

1. An improved cigarette paper comprising substantially purifiedcellulosic material and a hydrocarboncracking, activated siliceouscatalyst in powdered form in intimate association with said cellulosicmaterial.

2. The cigarette paper of claim 1 wherein the weight of the activatedsiliceous catalyst is in the range of about 20 to of the weight of thecellulosic material.

3. The cigarette paper of claim 1 wherein the activated siliceouscatalyst is an acid-treated clay.

4. The cigarette paper of claim 1 wherein the activated siliceouscatalyst is a synthetic catalyst comprising a major weight proportion ofsilica and a minor weight proportion of at least one ditficultlyreducible metal oxide.

5. The cigarette paper of claim 4 wherein the synthetic catalyst hasbeen prepared by the co-precipitation of the hydrous oxides of siliconand aluminum in a weight ratio of 9:1 of silica to alumina.

6. An improved cigarette paper comprising a major weight proportion ofsubstantially purified cellulosic material and a minor weight proportionof a hydrocarboncracking, activated siliceous catalyst in powdered formuniformly dispersed in said cellulosic material.

7. The cigarette paper of claim 6 wherein the activated siliceouscatalyst is an acid-treated clay.

8. The cigarette paper of claim 6 wherein the activated siliceouscatalyst is heat-treated montmorillonite.

9. The cigarette paper of claim 6 wherein the activated siliceouscatalyst comprises a major weight proportion of silica gel impregnatedwith a minor weight proportion of alumina.

References Cited in the file of this patent UNITED STATES PATENTS1,614,660 Darlington et al. Jan. 18, 1927 2,007,407 Sadtler July 9, 19352,460,285 Hale Feb. 1, 1949 2,466,051 Shakbaker et al Apr. 5, 1949FOREIGN PATENTS 1,218 Denmark Aug. 10, 1897

1. AN IMPROVED CIGARETTE PAPER COMPRISING SUBSTANTIALLY PURIFIEDCELLULOSIC MATERIAL AND A HYDROCARBONCRACKING, ACTIVATED SILICEOUSCATALYST IN POWDERED FORM IN INTIMATE ASSOCIATION WITH SAID CELLULOSICMATERIAL.